DESCRIPTION: (Applicant?s Description) The epothilones are a family of polyketide natural products produced by the myxobacterium Sorangium cellulosum. The epothilones bind to and stabilize microtubules in human cell lines leading to mitotic arrest and subsequently apoptosis. This feature makes these molecules very attractive anticancer agents. This proposal outlines experiments to quickly and efficiently produce practical quantities of a diverse library of epothilone analogs, using biosynthetic engineering. Heterologus expression of the epothilone biosynthesis gene cluster in E. coli followed by priming with natural and unnatural substrates will provide efficient access to practical quantities of epothilone-like analogues. These compounds can be further modified via chemical synthesis to obtain a large diverse set of analogs. The effects of the epothilone analogs on microtubule dynamics will then be investigated in vitro via video microscopy. The in vivo effect of these analogs on mitotic arrest will also be examined via fluorescence microscopy. This research will demonstrate the effectiveness of combining synthetic chemistry and biosynthetic pathways to generate diverse libraries of complex molecules, identify new highly active anticancer agents and illuminate the biological mechanism of action of the epothilone family of natural products.